1. Field of the Invention
The present invention relates to a trolley conveyor that conveys a conveyed material or article in suspension, and specifically to a trolley conveyor for use in an automobile manufacturing line for suspending a car body from the ceiling to convey it to various processing stages such as a welding stage, a coating stage, etc.
2. Description of the Related Art
Various conveyor systems have been employed in the past to convey articles and materials in suspension. These include the ceiling-hung trolley chain conveyor, disclosed in Japanese Laid-Open Utility Model Publication No. HEI-5-37759, in which a conveyor trolley provided with a hook for hanging a conveyed article is mounted to travel freely on a conveyor rail installed in suspension from a ceiling. A large number of the conveyor trolleys are linked by conveyor chains driven so that they circulate in a closed path. Another article-suspending conveyor is the power-driven mobile ceiling carriage that has wheels traveling on a rail suspended from the ceiling. Conveyed articles are hung from the carriage. Another system utilizes a drive means such as a chain feeder or belt feeder installed on a rail suspended from a ceiling. Still another system utilizes a slanted rail, on which hangers are conveyed by virtue of their own weight.
Various problems are encountered in the conventional conveyor systems.
In the ceiling-hung trolley chain conveyor, periodic lubrication of the chains is necessary. Moreover, the sliding of the chains on the conveyor rail increases the level of noise produced by the conveyor. In addition, the maintenance, of individual trolleys is a nuisance, and the removal of individual trolleys from the conveyor, which is sometimes necessary, is also a nuisance.
Also, in the conventional ceiling mobile carriage, a collector terminal is used to feed power to the motor that drives the wheels of the carriage. Sliding abrasion created at the collector terminal stirs up dust which adheres to the conveyed material and creates piled-up spots thereon. Periodic replacement of the collector terminals is necessitated, which is disadvantageous. Moreover, since the feeder line has to be laid throughout the total length of the rail, the construction cost is burdensome.
In a hanger conveyor system using a chain feeder or a belt feeder as the drive means, the system construction becomes complicated and the system also tends to be large in size. The complexity and large size of the construction contribute to increased noise production, higher installation cost, and increased maintenance requirements.
In the case of a hanger conveyor system that utilizes the weight of the conveyed articles to carry the articles along a declining rail by gravity, the conveyor structure, and especially the drive means, are simplified. However, such a conveyor is suitable only for relatively light weight conveyed materials and articles such as clothing, which do not require a large amount of power to be conveyed. The gravity-dependent conveyor structure is not applicable to the conveyance of very heavy conveyed articles such as car bodies, which requires much larger amounts of power.
The invention addresses the aforementioned disadvantages of conventional conveyor systems, and it is an object of the invention to provide a friction drive system trolley conveyor that securely conveys heavy conveyed materials and articles with low noise stably and without roll, i.e. without rotation about an axis extending in the direction of conveyor movement, that simplifies system construction, and that facilitates maintenance work.
To achieve the foregoing object, the friction drive system trolley conveyor in accordance with the invention comprises a conveyor rail having a circular cross-section, an upper side and an underside, the rail extending in a longitudinal direction along a conveyor line; multiple J-shaped rail suspension members that bear the underside of the conveyor rail at intervals along the longitudinal direction of the conveyor rail; multiple inverted J-shaped hook members that engage and move along the upper side of the conveyor rail in the longitudinal direction; a driven bar extending between the inverted J-shaped hook members, the driven bar suspending a conveyed material or article; and friction drive means disposed along the conveyor line, the friction drive means engaging both sides of the driven bar and effecting movement of the driven bar along the conveyor line.
In one preferred embodiment, the friction drive means comprises a friction roller which engages one side of the driven bar to effect movement of the driven bar along the conveyor line and an idler roller that contacts the driven bar on the side opposite to said one side to guide the driven bar.
Preferably, the friction drive means is supported by a holding frame freely pivoted to swing on a support shaft suspended from a location above the conveyor rail.
The conveyor rail may be hollow or solid, so long as it has a circular cross-section. However, the circular cross-section of the conveyor rail is preferably hollow for lightness and strength, and to make it easier for the rail to be laid out suitably along the conveyor line.
Insofar as the mutually engaging faces of the driven bar and the friction drive means are concerned, it is possible for the faces to be respectively concave and convex. However, for optimum power transmission efficiency, both sides of the driven bar are preferably flat and the friction drive means preferably comprises circular, cylindrical rollers that engage both sides of the driven bar along lines of contact.
Further, with regard to the layout of the friction drive means in the friction drive system trolley conveyor of the invention, from the consideration of simplifying the system construction, the friction drive means are not required to be laid out in one-to-one correspondence with the driven bars, and it is especially preferable that the friction drive means be concentrated where the greatest conveyance power is needed, such as a carrying-in area, curved corner, and carrying-out area, etc. in the conveyor line.
The friction drive system trolley conveyor of the invention thus constructed exhibits the following functions.
The friction drive system trolley conveyor includes the driven, load-supporting bar hung between inverted J-shaped hook members, and a friction drive means engaging both sides of the driven bar to move the driven bar in the conveying direction. A conveying force is imparted to the bar by the friction exerted between the drive means and the bar. Thus, the friction drive system trolley conveyor exhibits a so-called friction drive function.
Further, since the friction drive system trolley conveyor is provided with a large number of inverted J-shaped hook members that move longitudinally along the upper side of the conveyor rail, the inverted J-shaped carriers roll smoothly on, and in line contact with, the rail. This suppresses contact noises which are otherwise likely to be generated at the locations at which the conveyor is supported. Thus, the friction drive system trolley conveyor also exhibits a so-called contact noise suppressing function.
In addition, the conveyor rail, and the driven bar hung between the inverted J-shaped hook members, form a ladder-like parallel linkage in a vertical plane along the conveyor line, which stabilizes the pitch attitude of the conveyed material or article. Thus, the friction drive system trolley conveyor exhibits a so-called attitude stabilizing function.
Since the driven bars are hung between inverted J-shaped hook members, even though the driven bar is straight, it can smoothly follow the locus of the arc at the curved corners of a conveyor line, both ends of the driven bar being suspended, and the bar forming a chord. Thus, the friction drive system trolley conveyor exhibits a so-called arc line following function.
Since the friction roller engages one side of the driven bar to drive the bar in the conveying direction, and the passive roller engages the other side of the driven bar to guide it, and the two rollers embrace the bar on both sides, the conveying force is transmitted smoothly to the bar by the friction roller without loss. Thus, the friction drive system trolley conveyor also displays a so-called conveyance force loss prevention function.
Finally, since the friction drive means is supported by a holding frame pivoted to swing freely on a support shaft, the friction drive means is able to rectify dislocations and kinks in the holding state, by accommodating roll of the driven bar, and lateral translation thereof as the driven bar traverses a corner in the conveyor line. Thus, the friction drive system trolley conveyor also displays a so-called holding state rectifying function.